2 Sylvia S. Mader Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Immagini e concetti della biologia

3 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 A5 - Cellular Activity

4 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Energy is the ability to do work Radiant energy Chemical energy Mechanical energy Energy has different forms

5 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Radiant Energy (or solar energy) is the energy coming from the sun and is associated to electromagnetic waves. Chemical Energy is the energy contained into organic molecules in the form of specific chemical bonds. Mechanical Energy is the energy associated with any type of motion. Energy has different forms

6 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Heat is the energy related to the motion of microscopic systems such as atoms, ions and molecules. Calorie = the amount of energy needed to increase the temperature of 1 g of water by 1 °C. Energy has different forms

7 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Potential energy The energy of a body due to the position. Is a stored energy. Kinetic energy The energy of a body due to its motion. Is the energy in action. Potential energy or kinetic energy?

8 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Thermodynamics is a branch of sciences concerned with heat flows and its relations to energy and work. Principles applied to transformation of energy are know as “Laws of thermodynamics”. The two laws of thermodynamics

9 Solar energy Chemical energy Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 I law of Thermodynamics (or law of conservation of energy) “Energy can change form within the systems (solar energy can become chemical energy), but it can be neither created nor destroyed”. The two laws of thermodynamics

10 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The two laws of thermodynamics II law of Thermodynamics “Energy cannot change from one form to another without a loss of energy in the form of heat. This heat increases the entropy (disorder) of the system”. Solar energy Chemical energy HEAT

11 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Many important biological reactions involve a loss of energy as heat. The two laws of thermodynamics

12 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Energy flow and transformations

13 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 ATP (Adenosine Triphosphate) is a nucleotide that consists of: A double ring of carbon and nitrogen atoms called adenine; A small five-carbon carbohydrate called ribose; Three phosphate units linked together by covalent bonds. Adenine Ribos e Phosphate groups Cellular work is powered by ATP

14 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The breaking reaction products (ADP + P) are more stable than the molecule of ATP. Hence, when ATP breaks down to ADP + P, energy is released. ATP +ADP P Adenosine Triphosphate Adenosine Diphosphate Cellular work is powered by ATP

15 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 ATP ➞ ADP + P exergonic reaction (releases energy) ADP + P ➞ ATP endergonic reaction (requires energy to occur) ATP cycle

16 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 ATP hydrolysis is always associated with endergonic reactions. Reactions are coupled when the energy required for a reaction (endergonic) is provided by an exergonic reaction. Muscular contraction occurs if associated with ATP hydrolysis Coupled reactions

17 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Enzymes speed up the reaction by decreasing the energy of activation (E a ) of a given reaction. Enzymes are catalysts

18 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Substrate concentration Temperature pH Cofactors as vitamins and coenzymes Factors affecting enzymes activity

19 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Metabolic pathways are series of chemical reactions occurring within a cell. Metabolic pathways and inhibition Enzyme inhibition occurs when a substance binds to an enzyme and decreases its activity.

20 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Noncompetitive inhibition: inhibitor binds to an enzyme at the allosteric site (a site other than the active site). Competitive inhibition: an inhibitor and a substrate compete for the enzyme’s active site. In the case of some inhibitors such as cyanide, sarin gas or warfarin (rat poison) enzymatic inhibition can spell death. Enzyme inhibition

21 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Proteins are embedded in a phospholipid bi-bilayer in a “fluid mosaic membrane”. Plasma Membrane is dynamic

22 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Channel and carrier proteins respectively allow and assist the passage of molecules through the membrane. Membrane Proteins have various functions

23 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Cell recognition proteins help the cell recognize foreign invaders. Receptor proteins bind specific molecules. Membrane Proteins have various functions

24 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Enzymatic proteins carry out metabolic reactions while junction proteins assist cell-to-cell communications. Membrane Proteins have various functions

25 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Some small molecules or ions such as CO 2, O 2, C 6 H 12 O 6 and H 2 O, move across the plasma membrane by diffusion, a passive transport process. There are two types of diffusion: Simple diffusionFacilitated diffusion Diffusion

26 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Molecules in solution move down a concentration gradient until they equally distribute. Simple diffusion

27 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Carrier proteins facilitate diffusion of nonlipid-soluble substances across the membrane. Facilitate diffusion does not require energy. Facilitate diffusion

28 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Water moves into a region of higher solute concentration, in order to equalize the solute concentrations on the two sides of the membrane. Osmosis

29 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Cells placed in an isotonic solution (iso = same) neither gain nor lose water. Cells place in a hypotonic solution (ipo = less) gain water. Cells placed in a hypertonic solution (iper = more) lose water. Osmosis effects on animal and plant cells Osmosis

30 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 In order to move a substance against its concentration gradient the consumption of energy (ATP) is required. Carrier proteins involved in active transport are called pumps. Active transport

31 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Endocytosis is the process by which cells absorb big particles by engulfing them. Most biologically important substances are large molecules that cannot pass through the plasma membrane. Endocytosis

32 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Transport of massive particles (macromolecules) in and out the cell membrane requires the use of vesicles. Exocytosis Exocytosis is the process by which vesicles transport substances as digestive enzymes and hormones out of the cell.

33 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Malfunctioning plasma membrane proteins can cause human diseases such as: Cystic fibrosis is caused by a malfunctioning gene of the channel protein called FC-protein malfunctioning FC- channel protein Accumulation of mucus in the respiratory tract H 2 O and Cl - are trapped inside the cell Diabetes type 2 Cystic fibrosis Color blindness Malfunctions in the membrane proteins